•Aggregate functions can be used for some group by clause in this case it will give summary information for that specific group.

Example: Display the maximum salary of all departments in company

SELECT department_id as Dept,

AVG(salary)as Avg

FROM employees

GROUP BY department_id

•Nested Group functions

Group functions can be nested to a depth of two

Example, display the maximum average salary

SELECT MAX(AVG(Salary))

FROM employees

GROUP BY department_id